Method and apparatus for fluidizing activation of particulate, granular, viscous and similar materials

ABSTRACT

System for fluidizing and agitating material by introducing modulated gas into the material to reduce the internal friction thereof.

United States Patent [1 1 Holm et al.

[ Sept. 11, 1973 METHOD AND APPARATUS FOR FLUIDIZING ACTIVATION 0F PARTICULATE, GRANULAR, VISCOUS AND SIMILAR MATERIALS [76] Inventors: Bengt Lennart Holm, Sagoliden l1;

Sven Ivan Arvid Tiirnmarck,

Rosentigen 5, both of Malmo, Sweden 22 Filed: Dec. 3, 1969 211 App]. N0.:881,65 l

Related US. Application Data [63] Continuation-impart of Ser. No. 788,111, Nov. 22,

1968, Pat. No. 3,519,310.

[52] US. Cl 3112/53, 222/195, 222/199 [51] Int. Cl. B65g 53/40 [58] Field 01 Search .Q 302/29, 52, 53, 35;

[56] References Cited UNITED STATES PATENTS 2,429,359 10/1947 Kassel 302/53 3,223,457 12/1965 Albert 302/53 3,519,310 7/1970 Holm 302/29 Primary Examiner--Evon C. Blunk Assistant Examiner-H. S. Lane Att0rney-Eugene E. Geoffrey, Jr.

[5 7 ABSTRACT System for fluidizing and agitating material by introducing modulated gas into the material to reduce the internal friction thereof.

8 Claims, 7 Drawing Figures PATENTED 3,758,162

saw u or 5 INVENTORS v BENGT LENNART HOLM SVEN IVAN ARVID TORNM RCK ATTQR PATENTEBSEPHW 3,758,162

' sum 5 or s INVENTORS PATENTEDS'EPI I915 3'. 758. 162

sum s or 6 BENGT LENNART HOLM SVEN IVAN ARVID TORNMARCK METHOD AND APPARATUS FOR FLUIDIZING ACTIVATION F PARTICULATE, GRANULAR, VISCOUS AND SIMILAR MATERIALS CROSS-REFERENCE TO RELATED APPLICATIONS The present invention relates to a method and apparatus for fluidizing activation of particulate, granular,

viscous and similar materials and is a continuation-inpart of U.S. Letters Pat. No. 3,519,310 granted July 7, 1970 and filed Nov. 22, 1968 as a continuation of U.S. Pat. application Ser. No. 652,538, filed July I l, 1967, now abandoned.

BACKGROUND OF THE INVENTION This invention relates to the activation of particulate, granular, viscous and similar materials and more particularly to a novel and improved system for reducing the internal friction of such materials in order to agitate the material or to facilitate the flow thereof when removing material by gravity from containers and other storage spaces and when transporting material by gravity along slip planes and chutes. The system according to the invention is useful among other things for efficient removal of cement, chalk, starch, sand and other different types of particulate and granular materials as well as mortar, concrete and other different types of viscous materials from containers, such as tanks, drums, silos and the like.

Economical aspects impose the necessity of removing and transporting materials rapidly, e.g. when unloading and loading vehicles and vessels, and also of exploiting the maximum capacity of a generally cylindrical, spherical, or parallelpipedonal storage space to be emptied.

Many systems have heretofore been suggested for a rapid emptying of containers such as the use of air under pressure to act upon the material so that there is added to the weight thereof a force directed toward a discharge opening, which is generally located at the container bottom, and the use of vacuum which acts in a similar manner. In these prior art systems it is inevitable that the material is restrained to a certain extent during emptying because of the internal friction of the material, i.e., in a particulate or granular material the friction between the particles or granules thereof, particularly in a zone in the immediate vicinity of the discharge opening.

Another difficulty heretofore encountered with known systems utilizing compressed air for emptying containers is the effect known as the rat hole effect. When compressed air is introduced into the bottom of a container having an outlet, the particulate material immediately above the outlet will begin to flow therethrough. This process continues until a vertical hole is formed above the outlet whereupon the compressed air merely flows beneath the material and into the outlet without functioning to remove further material from the container.

SUMMARY OF THE INVENTION This invention provides an improved system for fluidizing activation of particulate, granular, viscous and similar materials in order to loosen up the material and thereby to agitate the material or to cause it to flow freely.

According to the invention there is provided a method for the .purpose described in the preceding paragraph comprising the steps of blowing gas into the material to loose up the material and modulating the gas by a frequency to reduce the internal friction of the material.

The invention also provides an apparatus for practicing said method comprising means for introducing compressed gas into the material and means for modulating such gas to activate the material and thereby to reduce the internal friction thereof.

The modulation of the gas may be attained by modulating the gas introduced in said material to be activated at one or more frequencies, preferably within the audio frequency band. Frequencies between and 1,000 cps have proved particularly well suited to attain a good effect and a thorough penetration of the material.

BRIEF DESCRIPTION OF THE DRAWINGS In order that the invention may be fully understood, it will now be described with reference to the accompanying drawings in which:

FIG. 1 is a diagrammatical cross sectional view of a container provided with an emptying system according to the invention;

FIG. 2 is a side elevational view of a practical. embodiment of a container provided with an emptying system according to the invention;

FIG. 3 is an enlarged fragmentary vertical cross sectional view of the container in FIG. 2 at a discharge opening thereof and showing also sound transmitters associated therewith;

FIG. 4 is a fragmentary plan view of the arrangement shown in FIG. 3;

FIG. 5 is an elevational view, partly in vertical cross section, of a container provided with an emptying system according to the invention showing another embodiment of the transmitter arrangement;

FIG. 5A is an elevational view, partly in vertical cross section, of acontainer provided with an emptying system according to the invention showing a modification of the sound transmitter arrangement of FIG. 5;

FIG. 5B is a fragmentary plan view of the arrangement shown in FIG. 5A;

DESCRIPTION OF PREFERRED EMBODIMENTS In order to explain the principle of the method according to the invention reference is made to FIG. 1 in the accompanying drawings illustrating diagrammatically one example of apparatus for carrying out the method of the invention. In FIG. 1 there is shown in vertical cross section a storage container 11 of parallelepipedonal form filled with material. Arranged in this container is a perforate slip plane 12 covered with fabric, cloth or like material 12A on the upper side thereof. Slip plane 12 forms the material supporting surface of the container and slopes at a small angle or toward a discharge opening 13 at the bottom of the container for the removal of material therefrom. A high power sound transmitter 14 having a pneumatic dia-.

phragm or reed is mounted on the container and is directed into the interior thereof beneath the slip plane said sound transmitter being supplied with air under pressure through a pipe 15. An air supply pipe 16 is also connected to the interior of the container beneath the slip plane. However, the provision of air supply pipe 16 is optional.

The air energizing the sound transmitter 14 and exiting from the resonance horn or other resonator of the sound transmitter together with air supplied through pipe 16 flows through the air-permeable slip plane 12 and up into the material in the container in a highly modulated state created by the sound transmitter producing sound waves having a frequency which is preferably 100 to 1,000 cps. By the modulated air thus blown into the material in container 11 such material is fluidized and activated in a bottom layer 17. It is believed that this marked fluidizing and activating effect is produced by the modulation of the air which is caused thereby to penetrate the material and prevents the bottom layer 17 from compacting even though the particulate material is of the type that is hard to cause to flow by gravity on account of tendency of arc formation as is the case with cement, chalk and starch and other fine grain particulate material. Thus the internal friction of the material activated in the manner described is substantially reduced and the material flows by gravity along the slip plane 12 towards discharge opening 13 to be removed from the container through such openmg.

It has been established that with the system according to the invention it is possible to reduce the inclination of slip plane 12 from earlier commonly used values of 2045 down to about For comparison the slope angle when emptying is performed by prior art systems has been marked in FIG. 1 by a dash-and-dot line 18. The angle of inclination thereof is designated B The reduction of the slope angle thus achieved according to this invention affords considerable economical saving by more efficient utilization of the capacity of the container such as silos, mobile containers and cargo holds of vessel and containers of any other type and for different purposes.

It is to be understood that in certain cases sound transmitter 14 or similar modulating means may be used to achieve the desired result without the supplementary supply of compressed air through pipe 16. In other cases it may be desirable to use unmodulated air supply in combination with the air supplied through the sound transmitter the total air flow through airpermeable slip plane 12 being modulated by the sound waves propagating from sound transmitter 14.

Several sound transmitters in parallel may be associated with one and the same container. Generally the gas employed will be pressurized air but the use of other pressurized gas or gas mixture is of course conceivable in special cases, for instance when the material to be emptied from the container is sensitive to the oxygen of the air.

Referring to FIGS. 2-4 in the drawings a practical embodiment of a container having a system in accordance with the principles explained with reference to FIG. 1 now will be described in more detail. A cylindrical container having substantially hemispherical ends is mounted by shock and vibration absorbing members 21 fitted to the container by brackets 22, on elements 23 supported by a stationary structure or a mobile structure such as a vehicle or a vessel. At the top of the container are provided two conventional fill caps 24. The bottom of the container is provided with two mutually spaced discharge hoppers 25 each arranged adjacent one end of the container and terminating in a circular outwardly projecting flange 26. Slip plates 20A are provided in the interior of container 20 between hoppers 25 to span the horizontal bottom surface of the container. Connected with each hopper 25 is a curved closure member 27 having a circular outwardly projecting flange 28 at the marginal edge thereof, which is secured to flange 26 by stud bolts having upper and lower nuts 26A and 28A respectively. As shown in FIGS. 3 and 4 closure member 27 has a central apertured block 29 forming a central discharge opening of the closure member said opening communicating with a discharge tube 30 secured to block 29. Between block 29 and flange 28 extend a'plurality of radial cross bars 31 having flat rectangular cross section and outer ends of said cross bars being received in a circular recess 32 in the upper surface of flange 28. The cross bars are covered by a layer 33 of fabric, cloth or other similar air-permeable material extending over the upper surface of flange 28 to the outer periphery thereof and clamped at its outer marginal portion between flanges 26 and 28. At their inner ends cross bars 31 and an inner marginal portion of layer 33 define a central opening in said layer, registering with the central opening in block 29, and are clamped between the upper surface of block 29, which forms a conical recess having a bottom sloping toward the central opening formed by said block, and a conical collar 34 secured to block 29 by means not shown, e.g. countersunk screws having their heads flush with the upper surface of the collar and engaging tapped blind holes in block 29. Suitable packing material may be placed between cross bars 31 and block 29 as indicated at 35. Thus it will be seen that each discharge hopper 25 is closed at the lower end thereof by an air-permeable bottom forming a conical slip plane sloping from the peripheral wall of said hopper towards the discharge opening in block 29.

Communicating with space 27A defined by closure member 27, layer 33, flange 28, and block 29, are two tubes 36 having a substantially horizontal branch 36A closed at one end by a plate 37 and an upwardly inclined branch 36B extending from the other end of branch 36A and communicating with space 27A. Plate 37 forms a mounting member for a sound transmitter 38 of the pneumatic membrane or reed type which has the operating mechanism outside said plate and the resonance horn inside the plate and extending along branch 36A. To each sound transmitter is connected an air supply pipe 39, and the plurality of pipes 39 are connected to an air supply manifold 40 having a coupling 41 at one end for connection to an air compressor. Thus it is seen that sound frequency modulated air is supplied by the sound transmitters 38 to the interior of container 20 beneath the air-permeable bottom 31, 33 and passes through said bottom to penetrate into particulate or similar material supported thereby in the container as is indicated by arrows in FIG. 3. The fluidizing activation of the material as described in connection with FIG. 1 thereby is obtained, and the flow of material by gravity towards the central discharge opening thus is facilitated. However, it may be necessary to supply additional air through the material beyond that supplied by the sound transmitters, and for this purpose there is connected to space 27A a pipe 42 which is branched from a manifold 43 supported by container 20 on brackets 44. The manifold is closed at one end by a shut-off valve 45A and is provided with a coupling 458 at the other end to be connected to the air compressor. The communication between manifold 43 and each pipe 42 is regulated individually by a valve 46. As explained in connection with FIG. 1 the additional air supplied through pipes 42 is modulated by the sound waves propagating from the sound transmitters and contributes to the fluidizing of the material. The material entering the discharge opening in block 29 is carried by air flow from container through pipe 30 communicating with said opening. Pipes 30 join to have a common outlet 30A provided with coupling means for the connection of. pipe, hose or similar conduit means.

According to the invention there is provided for the system described with reference to FIGS. 2-4 an electrical indicating circuitry which is schematically shown in FIG. 2 and now will be described with reference to said FIGURE.

On the outer surface of container 20 there is fixed a detector 47 which is sensitive to sound within the frequency range used for the modulation of the activating.

air and produced by sound transmitters 37, and this detector is adapted to generate an electrical signal in response to the pick-up of sound within said range. Detector 47 is connected by a line 48 to adevice 49 controlled by the electric signal generated by the detector e.g. an amplifier or a relay which is supplied with elec tric power by a line 50 from suitable power source not shown in the drawing. Device 49 is connected by a line 51 with suitable indicating apparatus 52 which may include an audio indicator such as a bell or a born, a visual indicator such as a lamp, or a coil controlling an indicator of any other type as is shown diagrammaticallyin FIG. 2. Detector 47 and/or device 49 provide a threshold function, i.e. a signal is transmitted to indicating apparatus 52 only when the sound picked up by detector 47 is of an intensity greater than a predetermined value. This thresholdvalue may be determined by the characteristics of the detector which may be an electro-mechanical or electronic transducer, or by the characteristics of device 49. When container 20 is more or less filled with material and is being emptied, the sound produced by sound transmitters 38 as picked up by detector 47 is attenuated by the bulk of material supported by bottom 31, 33. The threshold value of the indicating circuitry may be adjusted in such manner that no indication is given when the detector picks up soundthat has been attenuated by the bulk of material.

However, when the container is empty or substantially empty there is little if any material stored in the container, between the sound transmittersa'ndthe detector which means that the sound picked up by the detector will have a relatively greater intensity when the container. is empty or is about to become empty. Thus, it

is possible to adjust empirically the threshold value of the indicating system so asto produce an indication only when the container is empty or is about to become empty. 5

As will be seen, the indicating circuitry described above and disclosed'in FIG. 2 provides simple means to indicate a substantially empty condition of the container. This circuitry may be applied to the container without it being necessary to intrude upon the space in the container or to pierce the wall thereof. If desirable the signal supplied'by detector 47 may be transmitted over a telephone line for remote control purposes.

The embodiment according to FIG. 5 comprises a substantially spherical container 53 of a common type having a fill cap 54 providing a central discharge openirig 55 at the bottom thereof, a discharge tube 56 being connected to said opening. Means for mounting the container movable or stationary may be provided e.g. as shown in FIG. 2. In the interior of the container there is provided a supporting structure consisting of an annular set of inclined legs 57 connected to the container at their lower ends and converging towards their upper ends, and a horizontal platform 58 connected to said legs at their upper ends. Supported by the supporting structure is a sound transmitter 59 of the pneumatic membrane type having an air supply pipe 60 extending to the exterior of the container to be connected to an air compressor. A set of several sound transmitters may be provided if desired. As will be seen in the drawing the sound transmitter has the operating mechanism disposed on the upper side of the platform, the resonance horn being disposed below the platform and extending axially on the vertical central axis of the container towards the discharge opening 55. On brackets 61 secured one on each leg 57 at the lower endthereof is mounted an inverted conical metal sheet member 62 which is arranged coaxially with the discharge opening of the container the tip or apex thereof being directed towards the discharge opening. The lower surface of member 62 defines together with the inner surface of the bottom of the container a conical space 63 surrounding discharge opening 55 and having a bottom sloping down towards such opening. The upper side of member 62 forms a cup which is covered by a perforate metal cover plate 64 joining the marginal edge of conical member 62 and defining a space 65 together with said member. Cover plate 64 is provided with a layer 66 of cloth, fabric or similar material on the upper side thereof. As is realized the perforated cover plate may be substituted by a cross bar structure as that disclosed in FIGS. 3 and 4 extending between andsupported by the resonance horn of sound transmitter 59 and the marginal edge of member 62. Preferably, there is arranged in the cover plate andthe layer thereon a central opening registering with the outlet opening of the resonance horn of sound transmitter 59 in order that the perforate plate and the layer thereon will not attenuate the sound produced by the sound transmitter. A

tube 67 extending through the wall of the container is connected to space 65 and provides for the supply of unmodulated air to said space.

As will be seen the system disclosed in FIG. 5 will operate in the same manner as those of FIGS. 1-4 and in accordance with the principles of the invention. When the container is to be emptied the material therein is activated and fluidized by air supplied through sound transmitter 59 and tube 67 into space 65and modulated by sound frequency.wavespropagating from the sound transmitter. The modulated air passes through perforate plate 64 and layer 66 andlpenetrates intothe material supported thereon, as is indicated by arrows in FIG. 5. Thusthe internal friction of the material in the container is reduced in the manner earlier described herein and the material will flow easily by gravity through space 63 towards the discharge opening 55' into discharge tube 56 as is also indicated by arrows in FIG. 5.

The embodiment disclosed in FIG. 5 and described above has the advantage that the sound transmitter or a plurality of sound transmitters arranged inside the container are surrounded by the material in the container when filled. This means that the sound produced by the sound transmitter or transmitters is attenuated by the surrounding material, the sound level in the immediate surroundings of the container thereby being reduced. Further, the sound activating system is out of the way when disposed inside the container which is substantially free of external apparatus for emptying the container.

In the embodiment of FIG. an indicating circuitry as that disclosed in FIG. 2 may be provided.

An improved form of the embodiment of FIG. 5 is disclosed in FIGS. 5A and 5B. In this form there is provided a pneumatic sound transmitter 159 having an air supply pipe 160 extending to the exterior of the container 153 to be connected to an air compressor in the manner described above. The supporting structure provided in the interior of the container to support the sound transmitter and elements connected therewith in the manner to be described, comprises two channel beams 158 disposed on opposite sides of the sound transmitter and connected at their ends to the inside of container 153 as by welding. Beams 158 are each connected with the sound transmitter by threaded studs 170 and nuts 171, said studs being formed by the end portions of bars 172 connected to an outwardly projecting circumferential flange 173 on sound transmitter 159 by nuts 174 screwed on said studs 170. Bars 172 extend vertically and are substantially parallel to the axis of a downwardly directed horn 175 forming part of sound transmitter 159, to an annular ring 176 surrounding said horn at the mouth thereof. Having passed through ring 176 bars 172 are angled outwardly and terminate in lugs 177. Two annular rings 178 and 179 are clamped together by bolts 180 having nuts 181 and passing through lugs 177 as well as both rings 178 and 179.

Between rings 178 and 179 there is clamped an inverted conical perforate metal sheet member 162 which is arranged coaxially with horn 175 and the discharge opening ]55 of the container, the top or apex thereof being directed towards the discharge opening. In the manner described above the lower surface of member 162 defines together with the inner surface of the bottom of the container a conical space 163 surrounding discharge opening 155 and having a bottom sloping down towards each opening. A conical perforate metal cover plate 164 covering the cup formed by member 162 is also clamped between rings 178 and 179 at the large diameter end thereof, the small diameter end of said cover plate being connected to the mouth of horn 175 by a ring 182 having pressure fit or being otherwise secured on the outside of the horn. Cover plate 164 is provided with an air permeable synthetic fiber cloth layer 166 on the upper side thereof such layer being secured between rings 178 and 179 and between horn 175 and ring 182 together with said cover plate. Bars 172 pass through tunnels on the upper surface of layer 166 formed by securing to said layer rectangular pieces 183, preferably of the same material as layer 166.

The embodiment according to FIGS. 5A and 5B operates in the same manner as that described with reference to FIG. 5, and the same advantages are achieved thereby. However, there is achieved in conical space 163 additional force downwards on the material passing through said space to discharge opening by means of the sound modulated air streams passing through the holes in the perforated metal sheet member 162.

Although the invention has been described with regard to the fluidizing of material in order to facilitate the flow of the material in connection with the removal or transport thereof it is contemplated that the system according to the invention may be applied in cases wherein flow of material is not required but the material has to be agitated to prevent compaction on the supporting surface.

The modulation of the air may be achieved by modulating the air before penetrating into the material to be activated as in the examples shown and described herein. However, it is possible to modulate the air or other gas penetrating into the material by enclosing the surface in which pressure modulations are produced, the air or other gas penetrating into the material is thus modulated by the modulated back pressure encountered thereby.

It is readily understood by those skilled in the art that the invention is not limited to practicing the method with the aid of the apparatus illustrated herein and that the invention can be carried into effect by other means within the scope of the appended claims.

We claim:

1. Apparatus for fluidizing particulate, granular, viscous and similar materials comprising a container for holding said material, including an outlet, a bottom in said container sloping toward said outlet, supplying means for introducing gas into said material, means for modulating the flow velocity of at least a portion of said gas prior to entrance into said material, said modulating means being disposed within said container, a lower gas permeable member in said container spaced from said bottom and defining together with said bottom a passage for said material from the interior of the container to said outlet, and an upper gas permeable member in said container, forming together with said lower gas permeable member a chamber and supporting material contained in the interior of said container above said chamber, said supplying means directing said modulated gas into said chamber, said gas being discharged from the chamber through said upper and lower gas permeable members to penetrate into said material thereby loosening and fluidizing the material.

2. Apparatus for fluidizing particulate, granular, viscous and similar materials comprising a container for holding said material, including an outlet, a bottom in said container sloping toward said outlet, supplying means for introducing gas into said material, means for modulating the flow velocity of at least a portion of said gas prior to entrance into said material, said modulating means being disposed within said container, a lower gas permeable member in said container spaced from said bottom and defining together with said bottom a passage for said material from the interior of the container to said outlet, and an upper gas permeable member in said container, forming together with said lower gas permeable member a chamber and supporting material contained in the interior of said container above said chamber, said supplying means directing said modulated gas into said chamber, said gas being discharged from the chamber through said upper and lower gas permeable members to penetrate into said material thereby loosening and fluidizing the material, said modulating means including a sound generator for producing pressure oscillations and an acoustic resonator horn associated therewith for modifying the pressure oscillav tions thus produced, said resonator horn opening into said chamber.

3. Apparatus according to claim 2 wherein said sound generator is disposed outside said chamber, and said acoustic resonator horn extends into said chamber through said upper gas permeable member, the opening of said horn facing said lower gas permeable membet.

4. Apparatus according to claim 1 wherein said upper gas permeable member comprises substantially rigid supporting means having openings therein for the passage of gas therethrough, and a gas permeable material overlying said openings.

5. Apparatus according to claim 1 wherein said lower gas permeable member comprises a perforate metal sheet member.

6. Apparatus according to claim 2 wherein said lower gas permeable member comprises an inverted conical perforate metal sheet member arranged co-axially with said resonator horn and said outlet and having the apex thereof directed toward the outlet, and wherein said upper gas permeable member forms a cover over the inverted conical member.

7. Apparatus for fluidizing particulate, granular, viscous and similar materials comprising a container for holding said material, including an outlet, a bottom in said container sloping toward said outlet, supplying means for introducing gas into said material, means for modulating the flow velocity of at least a portion of said gas prior to entrance into said material, said modulating means being disposed within said container, a lower gas permeable member in said container spaced from said bottomand defining together with said bottom a passage for said material from the interior of the container to said outlet, an upper gas permeable member in said container, forming together with said lower gas permeable member a chamber and supporting material contained in the interior of said container above said chamber, said supplying means directing said modulated gas into said chamber, said gas being discharged from the chamber through said upper and lower gas permeable members to penetrate into said material thereby loosening and fluidizing the material, and a sound responsive detector associated with said container and operable to detect said modulating frequency produced within the container, and indicating means operatively connected to said detector.

8. Apparatus for fluidizing particulate, granular, viscous and similar materials comprising a container for holding said material, including an outlet, the bottom of said container sloping toward said outlet, means disposed within said container for introducing gas into said material and for modulating the flow velocity of at least a portion of said gas prior to entrance into said material, said means including a sound generator for producing pressure oscillations and an acoustic resonator horn associated therewith for modifying the pressure oscillations thus produced, a lower gas permeable member in said container forming a cup and defining together with said bottom a passage for said material from the interior of the container to said outlet, and an upper gas permeable member in said container forming a cover on said lower gas permeable member and defining together therewith a chamber, said upper gas permeable member supporting material contained in the interior of said container above said chamber, said resonator horn opening into said chamber to supply said modulated gas to the interior thereof, such gas being discharged from the chamber through said upper and lower gas permeable members to penetrate into said material thereby loosening and fluiidizing the material. i l 

1. Apparatus for fluidizing particulate, granular, viscous and similar materials comprising a container for holding said material, including an outlet, a bottom in said container sloping toward said outlet, supplying means for introducing gas into said material, means for modulating the flow velocity of at least a portion of said gas prior to entrance into said material, said modulating means being disposed within said container, a lower gas permeable member in said container spaced from said bottom and defining together with said bottom a passage for said material from the interior of the container to said outlet, and an upper gas permeable member in said container, forming together with said lower gas permeable member a chamber and supporting material contained in the interior of said container above said chamber, said supplying means directing said modulated gas into said chamber, said gas being discharged from the chamber through said upper and lower gas permeable members to penetrate into said material thereby loosening and fluidizing the material.
 2. Apparatus for fluidizing particulate, granular, viscous and similar materials comprising a container for holding said material, including an outlet, a bottom in said container sloping toward said outlet, supplying means for introducing gas into said material, means for modulating the flow velocity of at least a portion of said gas prior to entrance into said material, said modulating means being disposed within said container, a lower gas permeable member in said container spaced from said bottom and defining together with said bottom a passage for said material from the interior of the container to said outlet, and an upper gas permeable member in said container, forming together with said lower gas permeable member a chamber and supporting material contained in the interior of said container above said chamber, said supplying means directing said modulated gas into said chamber, said gas being discharged from the chamber through said upper and lower gas permeable members to penetrate into said material thereby loosening and fluidizing the material, said modulating means including a sound generator for producing pressure oscillations and an acoustic resonator horn associated therewith for modifying the pressure oscillations thus produced, said resonator horn opening into said chamber.
 3. Apparatus according to claim 2 wherein said souNd generator is disposed outside said chamber, and said acoustic resonator horn extends into said chamber through said upper gas permeable member, the opening of said horn facing said lower gas permeable member.
 4. Apparatus according to claim 1 wherein said upper gas permeable member comprises substantially rigid supporting means having openings therein for the passage of gas therethrough, and a gas permeable material overlying said openings.
 5. Apparatus according to claim 1 wherein said lower gas permeable member comprises a perforate metal sheet member.
 6. Apparatus according to claim 2 wherein said lower gas permeable member comprises an inverted conical perforate metal sheet member arranged co-axially with said resonator horn and said outlet and having the apex thereof directed toward the outlet, and wherein said upper gas permeable member forms a cover over the inverted conical member.
 7. Apparatus for fluidizing particulate, granular, viscous and similar materials comprising a container for holding said material, including an outlet, a bottom in said container sloping toward said outlet, supplying means for introducing gas into said material, means for modulating the flow velocity of at least a portion of said gas prior to entrance into said material, said modulating means being disposed within said container, a lower gas permeable member in said container spaced from said bottom and defining together with said bottom a passage for said material from the interior of the container to said outlet, an upper gas permeable member in said container, forming together with said lower gas permeable member a chamber and supporting material contained in the interior of said container above said chamber, said supplying means directing said modulated gas into said chamber, said gas being discharged from the chamber through said upper and lower gas permeable members to penetrate into said material thereby loosening and fluidizing the material, and a sound responsive detector associated with said container and operable to detect said modulating frequency produced within the container, and indicating means operatively connected to said detector.
 8. Apparatus for fluidizing particulate, granular, viscous and similar materials comprising a container for holding said material, including an outlet, the bottom of said container sloping toward said outlet, means disposed within said container for introducing gas into said material and for modulating the flow velocity of at least a portion of said gas prior to entrance into said material, said means including a sound generator for producing pressure oscillations and an acoustic resonator horn associated therewith for modifying the pressure oscillations thus produced, a lower gas permeable member in said container forming a cup and defining together with said bottom a passage for said material from the interior of the container to said outlet, and an upper gas permeable member in said container forming a cover on said lower gas permeable member and defining together therewith a chamber, said upper gas permeable member supporting material contained in the interior of said container above said chamber, said resonator horn opening into said chamber to supply said modulated gas to the interior thereof, such gas being discharged from the chamber through said upper and lower gas permeable members to penetrate into said material thereby loosening and fluidizing the material. 